Door closers provide an automatic function of closing a door and help to ensure that doors are not inadvertently left open. Many conventional door closers are mechanically actuated and have a piston and one or more compression springs and ports. The compression spring provides the force for moving the door toward a closed position. A door closer is sized, or has a force setting, based on pre-loading of the compression spring with an initial bias in accordance with American National Standards Institute (ANSI) standards. ANSI standards specify the minimum force required to close a door as sizes 1 through 6, with 6 being the greatest closing force of the door closer.
During use of a door closer, the piston moves through a reservoir filled with a hydraulic fluid, such as oil. The piston is coupled to the door closer's arm such that, as the door is opened, the piston is moved in one direction and, as the door is closed, the piston is moved in the opposite direction. As the piston moves, it displaces hydraulic fluid, which may be forced through various ports. The force exerted by the door closer depends on loading of the compression spring and the speed of the action depends on the open or closed status of the ports. The ports are adjustable (open or closed) via needle valves that control flow of hydraulic fluid, and the compression spring setting may or may not be adjustable based on the construction of the door closer.
The compression spring must be set properly for a given door and installation. While some door closers are not adjustable and are designed to meet only one size, most are adjustable and cover the entire range of sizes 1 through 6. These must be adjusted during or after installation to meet the requirements of that particular opening. Commonly this is done by the manufacturer specifying a number of turns of a screw that extends from one end of the closer to pre-load the compression spring. Turning the screw in one direction increases the pre-load of the compression spring, while turning the screw in the other direction reduces the pre-load. There is no visible result external to the housing of the door closer from turning the screw. While certain attempts have been made at providing external indication of size, there exists a need for a door closer with a spring power setting indicator that improves ease of manufacture and installation.